Introduction: This study sought to investigate the effects of soft tissue on
measurements of a spinal vibration response using skin-mounted
accelerometers and a non-invasive contact tip.
Methods: Vibration was applied to the spine of porcine and human cadavers.
Measurements of the spinal vibration response were taken from needle, skin,
and bone-mounted accelerometers. Several skin-mounted accelerometer
placements dorsal to a spinous process were tested, and 6 different non-invasive
contact tip shapes were used to explore sources of variance in the signals.
Results: Vibration measured from skin-mounted accelerometers had altered
signal patterns compared to bone-mounted accelerometers. The measured FRF
was found to be sensitive to accelerometer positioning. No significant difference
in skin-bone correlation was attributed to contact tip shape or vertebral level.
Conclusion: The use of a non-invasive contact tip excites vibration in the soft
tissues which overlay the spine, in addition to the vertebral column. This
vibration interferes with skin sensor measurements of vertebral vibration
response, with the effect diminishing as distance from the contact tip increases.
Small changes in contact tip shape do not affect the correlation between skin
and bone signals.

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